This invention relates to an improved hydrocarbon conversion process which utilizes a solid phosphoric acid catalyst composition having a total silicon phosphate X-ray intensity greater than 40.0 percent relative to alpha-alumina and having been prepared by specific calcination conditions. In particular embodiments, the hydrocarbon conversion process comprises alkylation, oligomerization, hydration, and etherification of hydrocarbons and oxygenated hydrocarbons. Well-known products of said particular embodiments are high-octane gasoline, alcohols, and speciality chemicals such as xylene and cumene.
Solid phosphoric acid catalyst is especially well known for its usefulness in the hydrocarbon conversion processes of aromatic alkylation and olefin polymerization. The catalyst is composed of a support or substrate portion onto which is incorporated an acid fraction for catalytic activity. It is believed that the substrate portion is formed from the silica-phosphoric acid reaction, principally silicon orthophosphate, Si.sub.3 (PO.sub.4).sub.4, silicon pyrophosphate, SiP.sub.2 O.sub.7, as well as derivatives of these compounds. The catalyst is typically prepared by mixing silica with phosphoric acid followed by extrusion and calcination. The reactions are simply illustrated as follows: EQU 3SiO.sub.2 +4H.sub.3 PO.sub.4 .fwdarw.Si.sub.3 (PO.sub.4).sub.4 +6H.sub.2 O EQU SiO.sub.2 +2H.sub.3 PO.sub.4 .fwdarw.SiP.sub.2 O.sub.7 +3H.sub.2 O
The above reactions indicate that the phosphoric acid will react with silica to yield both types of phosphates depending upon stoichiometry and reaction conditions. The silicon orthophosphate can also be dehydrated during drying to give the silicon pyrophosphate, and this is believed to be the alternate mechanism for the silicon pyrophosphate formation. The silicon ortho- to pyrophosphate conversion also depends on factors such as temperature and hydration, as illustrated by the following equations: EQU Si.sub.3 (PO.sub.4).sub.4 +2H.sub.3 PO.sub.4 .fwdarw.3SiP.sub.2 O.sub.7 +3H.sub.2 O EQU Si.sub.3 (PO.sub.4).sub.4 +heat.fwdarw.2SiP.sub.2 O.sub.7 +SiO.sub.2
These reactions have made the catalyst manufacturing more complex. Low activity or low stability catalysts have resulted due to low crystallinity caused by poor crystallization conditions.